How Long Does It Take to Watch Restaurant to Another World?

There is a certain restaurant in the first basement level of a multi-tenant building in one corner of a shopping street near the office district. The historical restaurant, marked by a sign with a picture of a cat, is called "Western Cuisine Nekoya." This restaurant looks completely normal through the week, but on Saturdays, it opens in secret exclusively to some very unique guests. During these hours, doors in various areas of a parallel world open to allow customers of many different races and cultures into the restaurant.